This invention relates to energy absorbers used in conjunction with large structures to reduce the influence of externally induced motion on such structures.
Cyclic shear energy absorbing devices are known which employ the cyclic plastic deformation of certain materials beyond the elastic limit for the absorption of kinetic energy. Such absorbing devices are typically interposed between a building support member and a base member, or between two structural support members, in order to convert portions of the kinetic energy into heat in the absorbing material and thus reduce the motion imparted to the structure by externally induced forces, such as an earthquake or high winds. U.S. Pat. Nos. 4,117,637 and 4,499,694 describe and claim two such absorbing devices.
The present invention relates to a cyclic shear energy absorbing device which serves the same function as that in the aforesaid U.S. patents but which dissipates energy by an entirely different principle. In one preferred embodiment of the present invention a bearing similar to that described in the aforementioned U.S. patents has a core of granular material which is closely packed and confined so that when the bearing is subjected to cyclic shear energy frictional forces between the confined particles dissipate the energy.